Where does the Life Safety and Critical Circuit begin? 517.41(D)

[MEP_PM]

Where does the Life Safety and Critical circuit begin? I would normally say at the ATS. However, today I was shown a job in which the generator has two breakers (one for Life Safety and the other for Critical) at the generator. That leads me to where this could be become problematic depending on how this question is answered. The generator is being relocated and the existing underground duct bank intercepted and a new pull box is being installed. From there a new duct bank will be ran to the new generator location. So, do the life safety and critical feeders need to be separated in the pull box or 2 pull boxes used to comply with 517.41(D). This project is a nursing home project.

 

[Lady Engineer]

I've done a lot of Hospital jobs or healthcare (surgery centers), and the separation was always via the ATS.

Your 2 branches, Life safety & Critical care, need to be separated to provide back up power. Plus, one source is required to be normal power and the other a designated on-site emergency back up source.

There's no way to transfer from normal to emergency in the event of a power failure.

 

[MEP_PM]

To clarify, there are two ATS. The questions is physical separation of circuits. Does a pull box between the generator and ATS need to be divided to separate Life Safety and Critical feeders that connects the generator to the two ATS?

 

[roger]

In your scenario you need seperate raceways from the generator. The on board breakers would be the start of each Branch.


Roger